Shuttling hnRNPs control the fate of eukaryotic mRNAs throughout their journey from the active site of transcription to that of translation; thus, gain or loss of their function in hematopoietic cells might result in altered hematopoiesis and/or emergence of leukemia. In BCR/ABL-expressing cells, there is a marked increase in the levels of different RNA binding proteins including FUS, hnRNP A1, hnRNP E2 and hnRNP K, four shuttling hnRNPs involved in the regulation of mRNA biogenesis, processing, nuclear export, and translation. Ectopic expression and/or inhibition of the activity of FUS, hnRNP A1 and hnRNP E2 affects the proliferation, survival, and differentiation of normal and BCR/ABL-expressing cells, suggesting that enhanced expression/activity of certain RNA-binding proteins plays an important but as yet unrecognized role in BCR/ABL leukemogenesis. Thus, the objective of this proposal is: 1) To investigate the mechanisms regulating hnRNP E2 and hnRNP A1 expression/function in BCR/ABL-expressing cells. 2) To identify hnRNP A1 and hnRNP E2-associated mRNAs encoding proteins differentially expressed in CML-blast crisis and CML-chronic phase cells. 3) To determine the BCR/ABL-dependent mechanisms regulating the expression/function of hnRNP K and determine whether hnRNP K function(s) is(are) required for BCR/ABL-induced leukemogenesis.